Matter Is an atom really mostly empty space?Could I pull a single quark out of a proton?Why doesn't the floor fall through itself?Are particles really tiny balls?What's the smallest thing that exists?Where does my weight actually come from?
Light What is light, really?Why is the sky blue and the sunset red?How does a laser work?If light has no mass, why does gravity bend it?
Forces What is gravity, exactly?Why does a magnet stick?What holds an atomic nucleus together?If gravity is curved space, why talk about a gravity particle?
Quantum Can two electrons be in the same place?Can something really be in two places at once?Is randomness real or just our ignorance?What does 'observing' something actually do?Is an electron a point, or a cloud?
Space What is empty space actually made of?How big is universe?Are there extra dimensions hiding somewhere?How can galaxies move away faster than light?
Time Why does time only go forward?Could time travel actually be possible?Why does time pass faster as you get older?Does a photon experience time?
Cosmos If the inside and the outside of a black hole disagree, which one is right?Could I hold a small black hole?What was there before the Big Bang?How will universe end?How does the sun actually work?If energy is conserved, where does stretched light lose its energy to?
Edge Could everything we see be a simulation?Are we alone in universe?What can't physics explain?If space is woven out of entanglement, what is doing the entangling?Is there a limit to how much could ever be computed or known?
